Fossil preservation takes many different forms.
Identifying the preservation of fossilized remains means considering the route a dead ancient organism took to fossilization--how a carcass, say, instead of decomposing without visible trace, leaves some tangible evidence of its existence. An entire branch of scientific inquiry, called "taphonomy," concerns itself with the mysterious and prolonged interval between a living thing's expiration and the discovery of its fossil--if it manages to become fossilized at all, it is a comparatively rare occurrence. The fossilization itself involves different forms of preservation.
Instructions
1. Tree resin that entraps small creatures may transform into amber over time, preserving an interior fossil.
Identify amber-encased fossils by the obvious "mummies" of insects, arachnids, leaves and other biological remnants preserved in slabs of hardened tree resin. These fossils are some of the most intricate and complete, with the added benefit of being clearly visible within the fossilizing substance because of amber's transparency.
2. Look for fossils preserving "hard" portions of an organism in some reconstituted manner. This might include a recrystallized skeleton, wherein bone transforms into a more durable, long-lasting element through geologic warping of high pressure and temperature.
3. Skeletal remains can be reconstituted as fossils through chemical transformations.
Identify another kind of skeletal fossil that develops from dissolved substances in water through a process called permineralization. Water infiltrating sediments bedding a skeleton deposits precipitates that harden the bone or cartilage and mimic its structure. Similar processes with technical variations include petrifaction and replacement.
4. Fossil molds show a negative impression of an organism's remains.
Key out the hollow impressions of organic remains called molds, where the actual bones have decomposed but their outline has imprinted into sediments. A mold may generate a cast--a positive impression of the remains versus the mold's negative one--if other substances infiltrate its space and solidify as a replica of the original skeletal material.
5. Classify trace fossils as indirect evidence of a once-living organism's former presence. Some of the most widely known are so-called "fossil footprints," which can be identified as tracks preserved in some durable substrate for thousands or millions of years. (Some notable fossil footprints are those of early hominids or dinosaurs.) Other examples include fossil burrows, scratches and bite-marks.
Tags: different forms, fossil footprints
